Yes, you can paint on chocolate with Colour Mill.
Colour Mill's oil-based pigment coloring is specifically formulated to work with chocolate, buttercream, fondant, sugar paste, ganache, cake mix, swiss meringue, and other mediums containing fats or oils. This makes it an excellent choice for coloring and painting directly onto chocolate surfaces. It outperforms conventional gel coloring in these applications.
Therefore, using Colour Mill for painting on chocolate is a viable and effective technique.